Semiconductor light device and manufacturing method for the same

ABSTRACT

Provided is a semiconductor light device comprising a semiconductor substrate having a first conduction type; a first cladding layer having the first conduction type deposited above the semiconductor substrate; an active layer; a second cladding layer having a second conduction type; and a contact layer. The active layer includes a window portion that is disordered via diffusion of vacancies and a non-window portion having less disordering than the window portion, and the contact layer includes a first region and a second region that is below the first region and has greater affinity for hydrogen than the first region.

The contents of the following patent applications are incorporatedherein by reference:

No. 2011-083556 filed in Japan on Apr. 5, 2011,

No. 2011-083867 filed in Japan on Apr. 5, 2011, and

No. PCT/JP2012/001876 filed on Mar. 16, 2012.

BACKGROUND

1. Technical Field

The present invention relates to a semiconductor light device and amanufacturing method thereof.

2. Related Art

In a semiconductor laser element, in order to prevent damage known asCOD (Catastrophic Optical Damage) in the end surfaces through whichlight is input and output, a technique referred to as IFVD(Impurity-Free Vacancy Disordering) is known as a method for forming awindow portion with little laser light absorption by increasing thebandgap energy through disordering of the light input and outputsurfaces, as shown in Patent Document 1, for example.

Patent Document 1: Japanese Patent Application Publication No.2007-242718

However, with the conventional IFVD technique, it is difficult to keepthe degree of disordering in the non-window portion low whilemaintaining a high degree of disordering in the window portion.Therefore, it is difficult to restrict deterioration of the lasercharacteristics while preventing COD.

SUMMARY

Therefore, it is an object of an aspect of the innovations herein toprovide a semiconductor light device and a manufacturing method thereof,which are capable of overcoming the above drawbacks accompanying therelated art. The above and other objects can be achieved by combinationsdescribed in the claims. According to a first aspect of the presentinvention, provided is a semiconductor light device comprising asemiconductor substrate having a first conduction type; a first claddinglayer having the first conduction type deposited above the semiconductorsubstrate; an active layer deposited above the first cladding layer; asecond cladding layer having a second conduction type deposited abovethe active layer; and a contact layer deposited on the second claddinglayer. The active layer includes a window portion that is disordered viadiffusion of vacancies and a non-window portion having less disorderingthan the window portion, and the contact layer includes a first regionand a second region that is below the first region and has greateraffinity for hydrogen than the first region.

According to a second aspect of the present invention, provided is amethod of manufacturing a semiconductor light device, comprising forminga semiconductor layer including a first vacancy generating region thatgenerates vacancies and a vacancy diffusion encouraging region that hasa greater affinity for hydrogen than the first vacancy generating regionand encourages diffusion of the vacancies; depositing two types ofdielectric films having different densities on different regions of thesemiconductor layer; and through an annealing process, generatingvacancies with a density according to a density of the correspondingdielectric film in the first vacancy generating region, dispersing thegenerated vacancies in the semiconductor layer through the vacancydiffusion encouraging region, forming a first disordered region bydisordering a region of the semiconductor layer on which is depositedthe dielectric film having a lower density among the two types ofdielectric films, and forming a second disordered region having lessdisordering than the first disordered region on a region of thesemiconductor layer on which is deposited the dielectric film having ahigher density.

The summary clause does not necessarily describe all necessary featuresof the embodiments of the present invention. The present invention mayalso be a sub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a semiconductor laser element accordinga first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the semiconductor laser elementshown in FIG. 1.

FIG. 3 shows a step for describing the method for manufacturing thesemiconductor laser element according to the first embodiment.

FIG. 4 shows a step performed after the step shown in FIG. 3.

FIG. 5 shows a step of forming the window portion and the non-windowportion shown in FIG. 1.

FIG. 6 shows the window portion and the non-window portion formed by thestep shown in FIG. 5.

FIG. 7 shows a step performed after the step shown in FIGS. 5 and 6.

FIG. 8 shows a step performed after the step shown in FIG. 7.

FIG. 9 is a cross-sectional view of a modification of the semiconductorlaser element shown in FIG. 1.

FIG. 10 is a cross-sectional view of the semiconductor laser elementmanufactured according to the manufacturing method of the secondembodiment.

FIG. 11 shows a step for describing the method for manufacturing thesemiconductor laser element according to the second embodiment.

FIG. 12 shows a step performed after the step shown in FIG. 11.

FIG. 13 shows a step performed after the step shown in FIG. 12.

FIG. 14 shows a step performed after the step shown in FIG. 13.

FIG. 15 shows a step performed after the step shown in FIG. 14.

FIG. 16 is a cross-sectional view of a modification of the semiconductorlaser element shown in FIG. 10.

FIG. 17 is a planar view of an optical waveguide manufactured accordingto the manufacturing method of the third embodiment.

FIG. 18 is a cross-sectional view of the optical waveguide shown in FIG.17 over the line A-A.

FIG. 19 shows a step for describing the method for manufacturing theoptical waveguide according to the third embodiment.

FIG. 20 shows a step performed after the step shown in FIG. 19.

FIG. 21 shows a step performed after the step shown in FIG. 20.

FIG. 22 is a graph showing a relationship between the design values ofdoping amounts in the contact layer and the disordering in the windowportion and the non-window portion.

FIG. 23 is a graph showing the relationship between the total dopingamount of the contact layer and the disordering of the non-windowportion.

FIG. 24 is a graph showing the relationship between the total dopingamount of the contact layer and the disordering of the window portiondivided by the disordering of non-window portion, in a case where thereis a second region and a case where there is no second region.

FIG. 25 shows the relationship between disordering of the non-windowportion and a ratio of the threshold value in a case where IFVD isperformed and a case where IFVD is not performed.

FIG. 26 is a graph showing the hydrogen concentration of the vacancydiffusion encouraging region corresponding to the non-window portion andof the vacancy diffusion encouraging region corresponding to the windowportion.

FIG. 27 shows the relationship between the epitaxial growth temperatureof the vacancy diffusion encouraging region and the carbon concentrationand hydrogen concentration in the deposited film.

FIG. 28 shows the relationship between the growth rate for the epitaxialgrowth of the vacancy diffusion encouraging region and the C dopingconcentration and hydrogen concentration.

FIG. 29 shows the relationship between the flow rate ratio of thereactive gases during the epitaxial growth of the vacancy diffusionencouraging region, and the C doping concentration and hydrogenconcentration.

FIG. 30 shows the relationship between the dopant gas flow rate ratioduring the epitaxial growth of the vacancy diffusion encouraging region,and the C doping concentration and hydrogen concentration.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, some embodiments of the present invention will bedescribed. The embodiments do not limit the invention according to theclaims, and all the combinations of the features described in theembodiments are not necessarily essential to means provided by aspectsof the invention.

FIG. 1 is a perspective view of a semiconductor laser element 100according a first embodiment of the present invention. The presentembodiment describes an example in which the semiconductor light deviceis a semiconductor laser element, but the present invention is notlimited to this embodiment. The semiconductor laser element 100 may be aFabry-Perot resonant cavity laser having a ridge structure that confinesthe current in a striped pattern in the resonant cavity direction. Thesemiconductor laser element 100 includes a low reflection coating 10 anda high reflection coating 20 at the end surfaces formed by cleaving awafer. The high reflection coating 20 amplifies the laser light withinthe resonant cavity by reflecting the laser light. The low reflectioncoating 10 has a reflectivity with respect to the laser light that isless than that of the high reflection coating 20, and causes laser lightthat is resonated in the resonant cavity to be output to the outside asthe emitted light 30.

FIG. 2 is a cross-sectional view of the semiconductor laser element 100.The semiconductor laser element 100 includes a semiconductor substrate40 having a first conduction type, a buffer layer 42 having the firstconduction type, a first cladding layer 44 having the first conductiontype, a first guide layer 46 having the first conduction type, an activelayer 48, a second guide layer 50 having a second conduction type, asecond cladding layer 52 having the second conduction type, a contactlayer 54 deposited on the second cladding layer 52, an insulating layer56, an upper electrode 58, and a lower electrode 60.

The present embodiment describes an example in which the firstconduction type is n-type and the second conduction type is p-type, butinstead the first conduction type may be p-type and the secondconduction type may be n-type. The semiconductor substrate 40 having thefirst conduction type may be an n-type GaAs substrate. The n-type bufferlayer 42, the n-type first cladding layer 44, the n-type first guidelayer 46, the active layer 48, the p-type second guide layer 50, thep-type second cladding layer 52, the p-type contact layer 54, and theinsulating layer 56 are sequentially deposited on the surface of thesemiconductor substrate 40.

The upper electrode 58 is formed to cover the insulating layer 56. Theinsulating layer 56 includes an opening 57 in the top portion of thecontact layer 54. The contact layer 54 is in ohmic contact with theupper electrode 58 through the opening 57. The lower electrode 60 isformed on the bottom surface of the semiconductor substrate 40.

The semiconductor laser element 100 has a ridge structure in the shapeof stripes machined into a mesa shape in which the widths of the toplayer of the p-type second cladding layer 52 and the contact layer 54decrease as distance from the semiconductor substrate 40 increases. Dueto this ridge structure, the semiconductor laser element 100 confinesthe current injected into the active layer 48.

The n-type buffer layer 42 functions as a buffer layer for depositing anepitaxial layer with good crystallinity on the semiconductor substrate40. The buffer layer 42 has a lattice constant between the latticeconstants of the semiconductor substrate 40 and the first cladding layer44. The n-type buffer layer 42 may be an n-type GaAs layer.

The n-type first cladding layer 44 and the n-type first guide layer 46have their refractive indexes and thicknesses adjusted in a manner toconfine light in the layering direction. The refractive index of thefirst cladding layer 44 is less than the refractive index of the firstguide layer 46. The n-type first cladding layer 44 and the n-type firstguide layer 46 may include n-type AlGaAs layers. In this case, bysetting the Al composition of the n-type first cladding layer 44 to begreater than the Al composition of the n-type first guide layer 46, therefractive index of the n-type first cladding layer 44 can be made lessthan the refractive index of the n-type first guide layer 46. Thethickness of the n-type first guide layer 46 may be approximately 400μm, and the thickness of the n-type first cladding layer 44 may beapproximately 3 μm.

The active layer 48 may include a lower barrier layer 48 a, a quantumwell layer 48 b, and an upper barrier layer 48 c. The lower barrierlayer 48 a and the upper barrier layer 48 c confine carriers in thequantum well layer 48 b. The lower barrier layer 48 a and the upperbarrier layer 48 c may include AlGaAs layers that are not doped withimpurities. The quantum well layer 48 b may include an InGaAs layer thatis not doped with impurities. The recombination energy of the carriersconfined in the potential well structure is determined according to theIn composition and thickness of the quantum well layer 48 b. The activelayer 48 is not limited to having a single quantum well (SQW) structure,and may instead have a multiple quantum well (MQW) structure.

The p-type second guide layer 50 and the p-type second cladding layer 52form a pair with the n-type first guide layer 46 and the n-type firstcladding layer 44 described above, and have refractive indexes andthicknesses that are adjusted in a manner to confine light in thelayering direction. The p-type second guide layer 50 and the p-typesecond cladding layer 52 may include p-type AlGaAs layers. For example,by setting the Al composition of the p-type second cladding layer 52 tobe greater than the Al composition of the p-type second guide layer 50,the refractive index of the p-type second cladding layer 52 can be madeless than the refractive index of the p-type second guide layer 50. Thethickness of the p-type second guide layer 50 may be approximately 400μm, and the thickness of the p-type second cladding layer 52 may beapproximately 1 μm to 2 μm.

The contact layer 54 includes a first region 54 b and a second region 54a. The first region 54 b functions as a first vacancy generating regionthat generates vacancies when the window portion 62 is formed, asdescribed in detail further below. Specifically, the first region 54 bis a semiconductor layer having the second conduction type and dopedwith a first p-type dopant. The first region 54 b may be a p-type GaAslayer. Here, the first p-type dopant may be zinc (Zn), magnesium (Mg),or beryllium (Be). In order for the first region 54 b to realizereliable ohmic contact with the upper electrode 58, the first region 54b may be doped with a high concentration of Zn, e.g. approximately 1E+19(atoms/cm³).

The second region 54 a functions as a vacancy diffusion encouragingregion that encourages diffusion of vacancies when the window portion 62is formed. The second region 54 a has a greater affinity for hydrogenthan the first region 54 b. The second region 54 a may be formed with agrowth temperature lower than that of the first region 54 b. The greateraffinity for hydrogen in the second region 54 a may be realized bysetting a higher growth rate, increasing the amount of defects caused bydamage, increasing the flow rate of a hydrogen compound during growth,or increasing the hydrogen atmosphere when growth is stopped, forexample, for the second region 54 a with respect to the first region 54b.

The second region 54 a may be formed as a thin region at an interfacebetween semiconductor layers. The second region 54 a may be asemiconductor layer having the second conduction type and doped with asecond p-type dopant. The second region 54 a may be a p-type GaAs layer.The second p-type dopant has greater affinity for hydrogen than thefirst p-type dopant. The second p-type dopant may be carbon (C). Thesecond region 54 a is below the first region 54 b.

The total doping amount in the contact layer 54 is preferably no greaterthan 1.0E+15 (atoms/cm²). Here, the doping amount is an amount definedas the doping concentration (atoms/cm³) multiplied by the layerthickness (cm). The doping amount of the second region 54 a may be lessthan the doping amount of the first region 54 b.

The semiconductor laser element 100 includes the window portion 62 andthe non-window portion 64. The non-window portion 64 in formed in thelayers from the second cladding layer 52 to the buffer layer 42, in aregion below the contact layer 54. The window portion 62 is formed in aregion surrounding the non-window portion 64. The window portion 62 hashigher bandgap energy than the non-window portion 64, and is less likelyto absorb laser light than the non-window portion 64. The window portion62 includes a disordered portion formed by dispersing group IIIvacancies generated by the first region 54 b.

The active layer 48 includes the window portion 62 disordered by thediffusion of the vacancies and the non-window portion 64 having a lowerdegree of disordering than the window portion 62. The disordering of thewindow portion 62 may be at least five times that of the non-windowportion 64. Specifically, the disordering of the window portion 62 is noless than 25 meV, and the disordering of the non-window portion 64 is nogreater than 5 meV. With the semiconductor laser element 100, since thedisordering of the window portion 62 is less than the disordering of thenon-window portion 64, the deterioration of the laser characteristicscan be decreased while preventing the occurrence of COD.

The following describes an embodiment of a method for manufacturing thesemiconductor light device according to the present invention. Here, anexample is described in which the semiconductor laser element 100 isused as the semiconductor light device, but the semiconductor lightdevice is not limited to this. The semiconductor light devicemanufacturing method includes a step of forming a semiconductor layer, astep of depositing two types of dielectric films (first film 70 andsecond film 72) with different densities on different regions of thesemiconductor layer, and a step of forming a first disordered region anda second disordered region on the semiconductor layer via an annealingprocess. The semiconductor layer includes a first vacancy generatingregion that generates vacancies and a vacancy diffusion encouragingregion that encourages diffusion of the vacancies. The vacancy diffusionencouraging region has a greater affinity for hydrogen than the firstvacancy generating region. The annealing process causes the firstvacancy generating region to generate vacancies. The first vacancygenerating region generates vacancies with a density according to thedensity of the corresponding dielectric film. The generated vacanciesare dispersed in the semiconductor layer through the vacancy diffusionencouraging region. Among the two types of dielectric films (first film70 and second film 72), the first disordered region is formed bydisordering the region of the semiconductor layer on which is depositedthe dielectric film with the lower density (first film 70). The seconddisordered region having a lower disordering than the first disorderedregion is formed in the region of the semiconductor layer on which isdeposited the dielectric film having higher density (second film 72). Inthe present embodiment, the first disordered region includes the windowportion 62 and the second disordered region includes the non-windowportion 64.

FIGS. 3 to 8 show steps describing the method for manufacturing thesemiconductor laser element 100 according to the first embodiment. Asshown in FIG. 3, the step of forming the semiconductor layer includes astep of preparing the semiconductor substrate 40 having the firstconduction type, a step of sequentially depositing, on the semiconductorsubstrate 40 having the first conduction type, a plurality ofsemiconductor layers including the n-type buffer layer 42, the n-typefirst cladding layer 44, the n-type first guide layer 46, the activelayer 48, the p-type second guide layer 50, and the p-type secondcladding layer 52, and a step of depositing a contact layer 54 on thep-type second cladding layer 52. Each layer is sequentially deposited byusing an epitaxial growth technique such as metal organic chemical vapordeposition (MOCVD) or molecular beam epitaxy (MBE).

The step of depositing the contact layer 54 includes a step of formingthe vacancy diffusion encouraging region that encourages diffusion ofthe vacancies and a step of forming the first vacancy generating regionthat generates vacancies. In the present embodiment, the vacancydiffusion encouraging region is the second region 54 a and the firstvacancy generating region is the first region 54 b. The step of formingthe second region 54 a may include a step of deposition using epitaxialgrowth at a first temperature. The step of forming the first region 54 bmay include a step of deposition using epitaxial growth at a secondtemperature that is higher than the first temperature.

The step of depositing the first region 54 b using epitaxial growth atthe second temperature includes a step of doping with the first p-typedopant. The step of depositing the second region 54 a using epitaxialgrowth at the first temperature includes a step of doping with thesecond p-type dopant. The step of deposition using epitaxial growth atthe first temperature may be performed at a temperature that decreasesthe doping efficiency of the second p-type dopant relative to theincrease in the growth temperature. Here, the doping efficiency refersto the ratio of the doping concentration to the concentration of theactivated dopant. In other words, the depositing of the second region 54a using epitaxial growth is performed in a temperature range thatreduces the doping concentration of the dopant introduced in the filmrelative to the increase in the growth temperature.

Specifically, the first temperature is a temperature lower than 680° C.,e.g. a temperature of approximately 620° C. The second temperature is atemperature of 680° C. or more, e.g. a temperature of approximately 700°C. The present embodiment describes an example in which Zn is used asthe first p-type dopant and C is used as the second p-type dopant.

The step of depositing the contact layer 54 may be performed through asingle epitaxial growth step. In other words, the second region 54 a isdeposited by performing epitaxial growth with C as the dopant at thefirst temperature, and then the first region 54 b is deposited byperforming epitaxial growth with Zn as the dopant at the secondtemperature.

The second region 54 a contains the dopant C, which has a high affinityfor hydrogen (H), and is formed using epitaxial growth at the firsttemperature, and therefore the H is easily introduced in the film. Inother words, the second region 54 a has a higher hydrogen concentrationthan the first region 54 b. However, the surface of the second region 54a formed by epitaxial growth at the first temperature with a highconcentration of the C dopant has worsened crystallinity. Therefore, byperforming epitaxial growth with a high concentration of Zn at thesecond temperature, the crystallinity is improved and the contactresistance with the upper electrode 58 can be reduced.

The step of forming the second region 54 a may include a step ofepitaxial growth at a first growth rate. The step of forming the firstregion 54 b may include a step of epitaxial growth at a second growthrate that is lower than the first growth rate. The first growth rate maybe approximately 0.34 nm/s or more. As described further below, a highconcentration of H can be introduced in the film by increasing thegrowth rate of the film of the second region 54 a, and it is thereforepreferable to do so.

FIG. 4 shows a step following the step shown in FIG. 3. As shown in FIG.4, the step of depositing the two types of dielectric films withdifferent densities includes a step of depositing the two types ofdielectric films (first film 70 and second film 72) with differentdensities on different regions of the contact layer 54. First, an SiNfilm of 100 nm, for example, is deposited on the contact layer 54 usingcatalytic CVD, with silane gas and ammonia gas as the raw material. TheSiN film is deposited in a state where the flow rate of the rawmaterials silane and ammonia is ammonia-rich. After this, aphotolithography step and an etching step are performed to remove theSiN film outside of the region of the contact layer 54 corresponding tothe window portion 62, thereby forming the first film 70 on the regionof the contact layer 54 corresponding to the window portion 62. Sincethe first film 70 is deposited with N-rich conditions, the first film 70is a non-dense film. The film density of the first film 70 isapproximately 2.69 g/cm³, for example.

Next, a SiN film of 30 nm, for example, formed with Si-rich conditionson the first film 70 and the contact layer 54 is deposited usingcatalytic CVD. The second film 72 is deposited with Si-rich conditions,and therefore is a dense film. The film density of the second film 72 is2.79 g/cm³, for example. In other words, the second film 72, which is adense film having higher density than the first film 70, is formed onthe region corresponding to the non-window portion 64. A film made of amaterial other than SiN may be used as the dielectric film.

FIG. 5 shows a step following the step shown in FIG. 4. The step offorming the window portion 62 and the non-window portion 64 through theannealing process includes a step of making the hydrogen concentrationof the region of the second region 54 a corresponding to the non-windowportion 64 greater than the hydrogen concentration of the regioncorresponding to the window portion 62. The annealing process is a rapidthermal annealing (RTA) process performed at 915° C. for 30 seconds, forexample.

As described above, the hydrogen concentration of the second region 54 ais higher than that of the first region 54 b. When heated through theRTA process, the hydrogen 76 in the second region 54 a is absorbed inthe first film 70. As a result, the portion of the second region 54 acorresponding to the window portion 62 has a lower hydrogenconcentration. On the other hand, the hydrogen of the portion of thesecond region 54 a corresponding to the non-window portion 64 is noteasily absorbed by the second film 72, which is a dense film. In otherwords, as a result of the annealing process, in the second region 54 a,the hydrogen concentration of the region corresponding to the non-windowportion 64 is higher than the hydrogen concentration of the regioncorresponding to the window portion 62.

Internal vacancies caused by the separation of the hydrogen 76 aregenerated in the second region 54 a corresponding to the window portion62. Here, the internal vacancies refer to vacancies that are generatedby the absorption of the hydrogen 76 in the first film 70.

The Ga in the first region 54 b corresponding to the window portion 62is absorbed in the first film 70 as a result of the RTA process, andgroup III vacancies 74 are generated with a density depending on thedensity of the first film 70. In other words, the second region 54 agenerates internal vacancies that are separate from the group IIIvacancies 74. The group III vacancies 74 are dispersed from the surfaceside of the first region 54 b toward the second region 54 a.

The second region 54 a receives the group III vacancies 74 generated bythe first region 54 b. in the second region 54 a corresponding to thewindow portion 62, the group III vacancies 74 join together the internalvacancies, such that the vacancy concentration increases suddenly. Thegroup III vacancies 74 and the internal vacancies are dispersed all atonce from the second region 54 a in a direction of the active layer 48.In other words, diffusion of the group III vacancies 74 is encouraged bythe presence of the internal vacancies.

On the other hand, the H in the second region 54 a corresponding to thenon-window portion 64 is barely absorbed in the second film 72, which isa dense film, and there are fewer internal vacancies in this region thanin the second region 54 a corresponding to the window portion 62. The Gain the first region 54 b corresponding to the non-window portion 64 isbarely absorbed by the second film 72, which is a dense film. Therefore,there are fewer group III vacancies 74 in the first region 54 bcorresponding to the non-window portion 64 than in the regioncorresponding to the window portion 62. Accordingly, the active layer 48corresponding to the non-window portion 64 has a much lower disorderingthan the active layer 48 corresponding to the window portion 62.

FIG. 6 shows the window portion 62 and the non-window portion 64 formedby the step shown in FIG. 5. As a result of the step shown in FIG. 5,the window portion 62 is formed by disordering the active layer 48corresponding to the region where the dielectric film having the lowerdensity, from among the two types of dielectric films, is deposited andthe non-window portion 64, which has a lower disordering than the windowportion 62, is formed in the active layer 48 corresponding to the regionwhere the dielectric film having the higher density is deposited. As aresult, the absorption of laser light at the window portion 62 of theactive layer 48 is restricted to prevent the occurrence of COD, anddeterioration of the laser characteristics in the non-window portion 64is prevented.

FIG. 7 shows a step following the steps shown in FIGS. 5 and 6. As shownin FIG. 7, the semiconductor laser element 100 manufacturing methodincludes a step of forming a ridge structure. After the window portion62 and the non-window portion 64 are formed, the first film 70 and thesecond film 72 are removed. After this, a photolithography step and anetching step are performed to remove the upper portion of the contactlayer 54 and the p-type second cladding layer 52 in a striped pattern toform the ridge structure.

FIG. 8 shows a step following the step shown in FIG. 7. As shown in FIG.8, the semiconductor laser element 100 manufacturing method includes astep of depositing an insulating film on the contact layer 54 and thesecond cladding layer 52 and a step of forming electrodes. Theinsulating film is a silicon oxide film or a silicon nitride filmdeposited using CVD, for example. The step of forming the electrodesincludes a step of forming an opening 57 in the region contacting theupper electrode 58 via a photolithography step and an etching step, anda step of forming the upper electrode 58 over the entire top surface ofthe semiconductor substrate 40 and vapor-depositing the lower electrode60 over the entire bottom surface of the semiconductor substrate 40,through a sputtering step. Finally, the semiconductor substrate 40 iscleaved to form the low reflection coating 10 and the high reflectioncoating 20 on the cleaved surfaces, thereby completing the semiconductorlaser element 100.

FIG. 9 shows a semiconductor laser element 110 according to amodification of the semiconductor laser element 100. The semiconductorlaser element 110 differs from the semiconductor laser element 100 withrespect to the configuration of the contact layer 54. In comparison tothe contact layer 54 shown in FIG. 2, the first contact layer 54 of thesemiconductor laser element 110 further includes a third region 54 c.The third region functions as a second vacancy generating region. Thethird region 54 c has a p-type doping amount lower than that of thefirst region 54 b. The second region 54 a is provided between the firstregion 54 b and the third region 54 c.

The step of depositing the contact layer 54 includes a step ofdepositing the third region 54 c through epitaxial growth at a secondtemperature, prior to the step of depositing the second region 54 athrough epitaxial growth at the first temperature. The Zn doping amountof the first region 54 b may be 1E+19 (atoms/cm³), and the Zn dopingamount of the third region 54 c may be 1E+18 (atoms/cm³). The firstregion 54 b, the second region 54 a, and the third region 54 c areformed by a single epitaxial growth step.

FIG. 10 is a cross-sectional view of a semiconductor laser element 200manufactured according to a manufacturing method of a second embodimentof the present invention. Instead of having a ridge structure, thesemiconductor laser element 200 differs from the semiconductor laserelement 100 of the first embodiment by including a current confinementlayer 80. The semiconductor laser element 200 includes a semiconductorsubstrate 40 having a first conduction type, a buffer layer 42 havingthe first conduction type, first cladding layer 44 having the firstconduction type, a first guide layer 46 having the first conductiontype, an active layer 48, a second guide layer 50 having a secondconduction type, a second cladding layer 52 having the second conductiontype, a contact layer 54 deposited on the second cladding layer 52, acurrent confinement layer 80, a second contact layer 82, an upperelectrode 58, and a lower electrode 60.

In FIG. 10, components that have the same reference numerals ascomponents in FIG. 2 may have the same function and configuration asthese components as described in relation to FIGS. 2 to 9. In thesemiconductor laser element 200, the structure form the lower electrode60 to the second cladding layer 52 may be the same as the structure ofthe semiconductor laser element 100 from the lower electrode 60 to thesecond cladding layer 52.

The first contact layer 54 includes a second region 54 a formed throughlow-temperature epitaxial growth and doped with a high concentration ofC, and a first region 54 b formed through high-temperature epitaxialgrowth and doped with a high concentration of Zn, Mg, or Be. In thesecond region 54 a, the hydrogen concentration of the regioncorresponding to the non-window portion 64 is higher than the hydrogenconcentration of the region corresponding to the window portion 62.

The current confinement layer 80 is formed on the first contact layer54, and includes an opening 81 corresponding to the non-window portion64. The current confinement layer 80 may be an n-type GaAs layer. Thesecond contact layer 82 is deposited on the current confinement layer 80and the first contact layer 54 exposed by the opening 81. The secondcontact layer 82 includes a p-type GaAs layer doped with a highconcentration of Zn or Mg. The second contact layer 82 is in ohmiccontact with the upper electrode 58. The current confinement layer 80confines the current injected from the upper electrode 58, and improvesthe carrier density in the quantum well layer 48 b.

In the semiconductor laser element 200, the window portion 62 is formedin the region corresponding to the current confinement layer 80, and thenon-window portion 64 is formed in the region corresponding to theopening 81. In the semiconductor laser element 200, the effect of theinternal vacancies in the second region 54 a increases the disorderingof the window portion 62 in the quantum well layer 48 b of the activelayer 48 and decreases the disordering in the non-window portion 64.Accordingly, deterioration of the laser characteristics can berestricted while preventing the occurrence of COD.

FIGS. 11 to 15 show steps describing the manufacturing method of thesemiconductor laser element 200 according to the second embodiment ofthe present invention. In the same manner as the semiconductor devicemanufacturing method described above, the semiconductor laser element200 manufacturing method includes a step of forming a semiconductorlayer, a step of depositing two types of dielectric films (first film 70and second film 72) with different densities on different regions of thesemiconductor layer, and a step of forming a window portion 62 and anon-window portion 64 on the semiconductor layer via an annealingprocess. The step of forming the semiconductor layer includes a step ofpreparing a semiconductor substrate 40, a step of sequentiallydepositing, on the semiconductor substrate 40, a plurality ofsemiconductor layers including the n-type buffer layer 42, the n-typefirst cladding layer 44, the n-type first guide layer 46, the activelayer 48, the p-type second guide layer 50, and the p-type secondcladding layer 52, and a step of depositing the first contact layer 54on the p-type second cladding layer 52. Each layer is formed byepitaxial growth using MOCVD or MBE. The step of depositing the firstcontact layer 54 is the same as the step of depositing the contact layer54 shown in FIG. 3, and therefore redundant description is omitted.

After deposition of the first contact layer 54, an n-type GaAs layerthat will become the current confinement layer 80 is deposited on thefirst contact layer 54. On top of this layer, a SiO₂ film 84 is formedusing CVD, for example. Next, the SiO₂ film 84 in the regioncorresponding to the opening 81 is removed by a photolithography stepand an etching step.

FIG. 12 shows a step following the step shown in FIG. 11. As shown inFIG. 12, the etching step is performed with the SiO₂ film 84 as theetching mask, thereby forming the current confinement layer 80. Next,the SiO₂ film 84 serving as the etching mask is removed. An insulatingfilm other than the SiO₂ film 84 may be used as the etching mask.

FIG. 13 shows a step following the step shown in FIG. 12. The step ofdepositing the two types of dielectric films (70 and 72) with differentdensities includes a step of depositing the first film 70, which is anon-dense film, in the region corresponding to the window portion 62 anddepositing the second film 72, which is a dense film, in the regioncorresponding to non-window portion 64. This step is the same as thestep shown in FIG. 4, and therefore a redundant description is omitted.The step of forming the window portion 62 and the non-window portion 64on the semiconductor layer through an annealing process includes a stepof making the hydrogen concentration of the region corresponding to thenon-window portion 64 of the second region 54 a, which is the vacancydiffusion encouraging region, higher than the hydrogen concentration ofthe region corresponding to the window portion 62. As a result of theRTA process, the internal vacancies generated by the second region 54 acorresponding to the window portion 62 encourage diffusion of the groupIII vacancies generated by the first region 54 b corresponding to thewindow portion 62 and cause disordering of the active layer 48corresponding to the window portion 62. The active layer 48corresponding to the non-window portion 64 is not disordered. This stepis the same as the step described in FIGS. 5 and 6, and therefore aredundant description is omitted.

FIG. 14 shows a step following the step shown in FIG. 13. As shown inFIG. 14, the first film 70 and the second film 72 are removed. Next,surface cleansing is performed on the surfaces of the currentconfinement layer 80 and the first contact layer 54. As a result of thissurface cleansing, a decrease in the crystal quality at the regrowthinterface can be prevented.

FIG. 15 shows a step following the step shown in FIG. 14. As shown inFIG. 15, the p-type GaAs layer is regrown to form the second contactlayer 82. The second contact layer 82 may be deposited using epitaxialgrowth at a high temperature and doped with a high concentration of Znor Mg. The Zn doping concentration of the second contact layer 82 is1E+19 (atoms/cm³), for example. The Zn doping concentration of the firstcontact layer 54 is 1E+18 (atoms/cm³), for example.

Finally, the upper electrode 58 is formed on the second contact layer82, and the lower electrode 60 is formed on the bottom surface of thesemiconductor substrate 40. The upper electrode 58 and the lowerelectrode 60 may be formed by sputtering.

FIG. 16 shows a semiconductor laser element 210 that is a modificationof the semiconductor laser element 200. The first contact layer 54semiconductor laser element 210 of the present modification differs fromthe first contact layer 54 of the semiconductor laser element 200. Thefirst contact layer 54 of the semiconductor laser element 210 includes athird region 54 c that has a lower p-doping amount than the first region54 b. The second region 54 a is provided between the first region 54 band the third region 54 c.

The step of depositing the first contact layer 54 in the presentmodification includes a step of depositing the third region 54 c usingepitaxial growth at a second temperature, prior to the step ofdepositing the second region 54 a using epitaxial growth at a firsttemperature. The p-type doping amount of the third region 54 c is lowerthan that of the first region 54 b. The p-type dopant may be Zn, forexample. The Zn doping amount in the first region 54 b may be 1+E19(atoms/cm³) and the Zn doping amount in the third region 54 c may be1E+18 (atoms/cm³). The first region 54 b, the third region 54 c, and thesecond region 54 a are formed by a single epitaxial growth step.

FIG. 17 is a planar view of an optical waveguide 300 manufacturedaccording to the manufacturing method of a third embodiment of thepresent invention. FIG. 18 is a cross-sectional view over the line A-Aof FIG. 17. The optical waveguide 300 includes a semiconductor substrate310, and a semiconductor layer having a lower cladding layer 320, anoptical waveguide layer 330, and an upper cladding layer 340 formedsequentially on the semiconductor substrate 310. The semiconductor layerof the optical waveguide 300 includes a first disordered region 312 thatis selectively disordered in a direction perpendicular to the surface ofthe semiconductor substrate 310, and a second disordered region 314 thatis formed to be sandwiched by the first disordered region 312.

The disordering of the second disordered region 314 is less than thedisordering of the first disordered region 312. The disordering of thefirst disordered region 312 may be at least five times the disorderingof the second disordered region 314. Specifically, the disordering ofthe first disordered region 312 is 25 meV or more, and the disorderingof the second disordered region 314 is 5 meV or less. The bandgap energyof the first disordered region 312 is greater than the bandgap energy ofthe second disordered region 314. The refractive index of the firstdisordered region 312 is less than the refractive index of the seconddisordered region 314. In other words, the optical waveguide 300includes the first disordered region 312 and the second disorderedregion 314 having different disordering, and therefore, the opticalwaveguide layer 330 has a difference in refractive index with respect toa direction parallel to the semiconductor substrate 310 andperpendicular to the propagation direction of the light.

FIGS. 19 to 21 show steps describing the optical waveguide 300manufacturing process according to the third embodiment of the presentinvention. This manufacturing method includes a step of forming asemiconductor layer, a step of depositing two types of dielectric films(first film 370 and second film 380) with different densities ondifferent regions of the semiconductor layer, and a step of forming thefirst disordered region 312 and the second disordered region 314 in thesemiconductor layer through an annealing process.

FIG. 19 shows a step of forming the semiconductor layer. Thesemiconductor layer includes a vacancy generating region 360 thatgenerates vacancies and a vacancy diffusion encouraging region 350 thatencourages diffusion of the vacancies. The step of forming thesemiconductor layer includes a step of preparing the semiconductorsubstrate 310, a step of sequentially depositing on the semiconductorsubstrate 310 a plurality of semiconductor layers including the lowercladding layer 320, the optical waveguide layer 330, and the uppercladding layer 340, and a step of depositing the vacancy generating anddispersing region 362 on the upper cladding layer 340. These layers aresequentially deposited using an epitaxial growth technique such as metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy(MBE).

The step of depositing the vacancy generating and dispersing region 362includes a step of forming the vacancy diffusion encouraging region 350and a step of forming the vacancy generating region 360. The vacancydiffusion encouraging region 350 has a greater affinity for hydrogenthan the vacancy generating region 360. The step of forming the vacancydiffusion encouraging region 350 and the step of forming the vacancygenerating region 360 are the same as the step of forming the secondregion 54 a and the step of forming the first region 54 b described inFIG. 3, and therefore a redundant description is omitted.

FIG. 20 shows a step of forming dielectric films. The step of formingthe dielectric films includes a step of depositing two types ofdielectric films (first film 370 and second film 380) with differentdensities on different regions of the vacancy generating region 360. Thefirst film 370 is a non-dense film having a density that is less thanthe density of the second film 380. The second film 380 is a dense filmhaving a density that is greater than the density of the first film 370.The step of forming the first film 370 and the second film 380 is thesame as the step of depositing the two types of dielectric films (firstfilm 70 and second film 72) with different densities on differentregions of the contact layer 54 described in FIG. 4, and therefore aredundant description is omitted.

FIG. 21 shows the step of forming the first disordered region 312 andthe second disordered region 314 through the annealing process. As aresult of the annealing process, the vacancy generating region 360generates vacancies with a density depending on the density of thecorresponding dielectric films. The generated vacancies are dispersed inthe semiconductor layer through the vacancy diffusion encouraging region350. Among the two types of dielectric films (first film 370 and secondfilm 380), the first disordered region 312 is formed by disordering theregion of the semiconductor layer on which is deposited the dielectricfilm with the lower density (first film 370). The second disorderedregion 314 having a lower disordering than the first disordered region312 is formed in the region of the semiconductor layer on which isdeposited the dielectric film having higher density (second film 380).

In this step, the hydrogen concentration of the region corresponding tothe second disordered region 314 of the vacancy diffusion encouragingregion 350 is higher than the hydrogen concentration of the regioncorresponding to the first disordered region 312. The internal vacanciesare generated by separation of the hydrogen in the vacancy diffusionencouraging region 350 corresponding to the first disordered region 312.The Ga of the vacancy generating region 360 corresponding to the firstdisordered region 312 is absorbed in the first film 370 through theannealing process, and group III vacancies are generated according tothe density of the first film 370. The group III vacancies areencouraged to diffuse by the internal vacancies, and are dispersed inthe optical waveguide layer 330 through the vacancy diffusionencouraging region 350.

As a result, among the two types of dielectric films, the firstdisordered region 312 is formed by disordering the lower cladding layer320, the optical waveguide layer 330, and the upper cladding layer 340corresponding to the region on which the first film 370 having the lowerdensity is deposited. The second disordered region 314 having lessdisordering than the first disordered region 312 is formed on the lowercladding layer 320, the optical waveguide layer 330, and the uppercladding layer 340 corresponding to the region on which the second film380 having higher density is deposited.

FIG. 22 is a graph showing a relationship between the design values ofdoping amounts in the contact layer 54 of the semiconductor laserelement 100 and the disordering in the window portion 62 and thenon-window portion 64. In the following description, the doping amountrefers to an amount defined as the doping concentration (atoms/cm³)multiplied by the layer thickness (cm). Furthermore, the disorderingshows a change amount of the bandgap energy.

Designs 1 to 3 are examples using only Zn as the dopant. Designs 4 and 5are exampled using C and Zn as the dopants. Design 6 is an example usingonly C as the dopant. With designs 1 to 3, when the doping amount islower, the disordering of the non-window portion is lower and the ratioof the disordering of the window portion to the disordering of thenon-window portion is higher. Accordingly, the results of designs 1 to 3indicate that decreasing the total doping amount of the contact layer 54is effective.

When a comparison is made between designs 2 and 4, even though thedoping amount is the same, design 2 is doped with only Zn and design 4is doped with both Zn and C. When a comparison is made between thedisordering in designs 2 and 4, the disordering of the non-windowportion is lower and the ratio of the disordering of the window portionto the disordering of the non-window portion is higher in the case ofdoping with both Zn and C than in the case of doping with only Zn.Accordingly, the results of designs 2 and 4 indicate that using Zn and Cas the dopants is effective.

When a comparison is made between designs 4 and 5, the doping amount isgreater and the C ratio is higher than the Zn ratio in design 5 than indesign 4. When a comparison is made between the disordering of designs 4and 5, the disordering of the non-window portion, which has the lowerdoping amount, is lower but the ratio of the disordering of the windowportion to the disordering of the non-window portion is almostunchanged. Accordingly, the results of designs 4 and 5 indicate that itis effective to have a total doping amount of Zn and C that is nogreater than 1.0E+15 (atoms/cm²) and have a C doping amount that is lessthan the Zn doping amount.

When a comparison is made between designs 5 and 6, the doping amount isgreater in design 6 than in design 5, and design 6 is doped only with C.When a comparison is made between the disordering of designs 5 and 6,the disordering of the non-window portion increases drastically when thedoping amount increases, and the ratio of the disordering of the windowportion to the disordering of the non-window portion decreases when onlyC is used for doping. Accordingly, the results of designs 5 and 6indicate that it is effective to set the overall doping amount to be nogreater than a prescribed value and to combine C and Zn as the dopants.

FIG. 23 is a graph showing the relationship between the total dopingamount of the contact layer 54 and the disordering of the non-windowportion in the semiconductor laser element 100. Based on this graph itis understood that the disordering of the non-window portion increaseswhen the doping amount is increased. At a dopant concentration of 1E+15(atoms/cm²), which corresponds to design 5 in FIG. 17, the disorderingof the non-window portion is a favorable value of approximately 5 meV.

FIG. 24 is a graph showing the relationship between the total dopingamount and the disordering of the window portion divided by thedisordering of the non-window portion, in a case where the contact layer54 of the semiconductor laser element 100 includes the second region 54a and a case where the contact layer 54 does not include the secondregion 54 a. Based on this graph, when the doping amount is near a valueof approximately 1.2E+15 (atoms/cm²), the disordering of the windowportion divided by the disordering of the non-window portion isapproximately 2, regardless of whether the second region 54 a ispresent. When the doping amount decreases below approximately 1.2E+15(atoms/cm²), the disordering of the window portion divided by thedisordering of the non-window portion becomes greater than 2, and thedisordering of the window portion divided by the disordering of thenon-window portion is larger when the second region 54 a is includedthan when the second region 54 a is not included.

In other words, when the doping amount is less than approximately1.2E+15 (atoms/cm²) and the second region 54 a is included, thenon-window portion 64 can be formed with disordering that is less than ½the disordering of the window portion 62. When the doping amount is1E+15 (atoms/cm²), which is the doping amount of design 5 in FIG. 17,the non-window portion 64 can be formed with disordering that is lessthan 1/7 the disordering of the window portion 62, and therefore thisdoping amount is favorable.

FIG. 25 shows the relationship between disordering of the non-windowportion in the semiconductor laser element 100 and a ratio of the laseroscillation threshold voltage in a case where the window portion isformed by IFVD and a case where the window portion is not formed. Whenthe threshold ratio is 1 or less, deterioration of the laser performanceis restricted by the IFVD, and when the threshold ratio is greater than1, the laser performance is deteriorated by the IFVD. Based on thegraph, it is understood that the threshold value is approximately 1 whenthe disordering of the non-window portion is approximately 5 meV. Asdescribed above, the disordering of the non-window portion beingapproximately 5 meV corresponds to the case shown in FIG. 18 where thedoping amount is 1E+15 (atoms/cm²). The case in which the doping amountis 1E+15 (atoms/cm²) corresponds to design 5 in FIG. 17. The dopingamount may be set such that the disordering of the non-window portion isless than 4 meV.

Based on the experimental results shown in FIGS. 22 to 25, it isunderstood that the total doping amount of the contact layer 54 ispreferably no greater than 1E+15 (atoms/cm²). Furthermore, it isunderstood that the contact layer 54 preferably includes the secondregion and that the C doping amount is less than the Zn doping amount.

FIG. 26 shows a comparison of the hydrogen concentration between thewindow portion 62 and the non-window portion 64 of the second region 54a. It is understood that the hydrogen concentration of the windowportion 62 is approximately 40% of the hydrogen concentration of thenon-window portion 64. Based on the graph, it is understood that, as aresult of the RTA process, approximately 60% of the hydrogen of thesecond region 54 a corresponding to the window portion 62 is absorbed inthe first film 70, thereby generating internal vacancies.

FIG. 27 shows the relationship between the epitaxial growth temperatureof the second region 54 a, which is the vacancy diffusion encouragingregion, and the C dopant concentration and hydrogen concentration. Whenthe growth temperature is 680° C., the C doping amount is approximately1.44E+18 (atoms/cm³) and the H concentration is approximately 8.0E+16(atoms/cm³). When the growth temperature is 620° C., the C doping amountis approximately 5.68E+18 (atoms/cm³) and the H concentration isapproximately 5.8E+17 (atoms/cm³). When the growth temperature is 560°C., the C doping amount is approximately 2.42E+19 (atoms/cm³) and the Hconcentration is approximately 6.0E+18 (atoms/cm³).

Based on these results, it is understood that the C is introduced in thefilm with a high affinity for H, when the temperature range is such thatthe C doping efficiency decreases relative to an increase in the growthtemperature. Furthermore, it is understood that when the growthtemperature is lower, the C doping concentration is higher and thehydrogen concentration introduced in the film increases. Specifically,it is preferable to form the second region 54 a using epitaxial growthwith a low temperature no greater than 680° C. and with a high C dopingconcentration of 1.5E+18 (atoms/cm³).

FIG. 28 shows the relationship between the growth rate for the epitaxialgrowth of the second region 54 a, which is the vacancy diffusionencouraging region, and the C doping concentration and hydrogenconcentration. The growth temperature was set to a constant 560° C. Whenthe growth rate is approximately 0.34 nm/s, the C doping concentrationis 2.05E+19 (atoms/cm³) and the H concentration is 4.5E+18 (atoms/cm³).When the growth rate is approximately 0.66 nm/s, the C dopingconcentration is 2.42E+19 (atoms/cm³) and the H concentration is 6.0E+18(atoms/cm³). Based on these results, it is understood that the Hconcentration introduced in the film is increased by increasing the rateof the epitaxial growth of the second region 54 a. The epitaxial growthrate of the first region 54 b may be lower than the epitaxial growthrate of the second region 54 a.

FIG. 29 shows the relationship between the flow rate ratio of thereactive gases during the epitaxial growth of the second region 54 a,which is the vacancy diffusion encouraging region, and the C dopingconcentration and hydrogen concentration. The flow rate ratio of thereactive gases refers to the ratio of the flow rate of arsine (AsH₃)gas, which is a group V atom supply gas, to the flow rate oftrimethylgallium (TMG) gas, which is a group III atom supply gas. Thegrowth temperature was set to a constant 560° C. When the flow rateratio of the reactive gases is approximately 21.2, the C dopingconcentration is 1.06E+19 (atoms/cm³) and the H concentration is 1.5E+18(atoms/cm³). When the flow rate ratio of the reactive gases isapproximately 14.2, the C doping concentration is 1.49E+19 (atoms/cm³)and the H concentration is 2.6E+18 (atoms/cm³). When the flow rate ratioof the reactive gases is approximately 7.0, the C doping concentrationis 2.42E+19 (atoms/cm³) and the H concentration is 6.0E+18 (atoms/cm³).Based on these results, it is understood that the H concentrationintroduced in the film is increased by decreasing the flow rate ratio ofthe reactive gases.

FIG. 30 shows the relationship between the dopant gas flow rate ratioduring the epitaxial growth of the second region 54 a, which is thevacancy diffusion encouraging region, and the C doping concentration andhydrogen concentration. The dopant gas flow rate ratio refers to theratio of the flow rate of carbon tetrabromide (CBr₄) gas, which is the Cdopant gas, to the flow rate of trimethylgallium (TMG) gas, which is thegroup III atom supply gas. The growth temperature was set to a constant560° C. The reactive gas flow rate ratio was kept constant. When thedopant gas flow rate ratio is approximately 0.052, the C dopingconcentration is 1.49E+19 (atoms/cm³) and the H concentration is 2.6E+18(atoms/cm³). When the dopant gas flow rate ratio is approximately 0.103,the C doping concentration is 2.05E+19 (atoms/cm³) and the Hconcentration is 4.5E+18 (atoms/cm³). Based on these results, it isunderstood that the H concentration amount introduced in the film isincreased by increasing the dopant gas flow rate ratio.

While the embodiments of the present invention have been described, thetechnical scope of the invention is not limited to the above describedembodiments. It is apparent to persons skilled in the art that variousalterations and improvements can be added to the above-describedembodiments. It is also apparent from the scope of the claims that theembodiments added with such alterations or improvements can be includedin the technical scope of the invention.

The operations, procedures, steps, and stages of each process performedby an apparatus, system, program, and method shown in the claims,embodiments, or diagrams can be performed in any order as long as theorder is not indicated by “prior to,” “before,” or the like and as longas the output from a previous process is not used in a later process.Even if the process flow is described using phrases such as “first” or“next” in the claims, embodiments, or diagrams, it does not necessarilymean that the process must be performed in this order.

What is claimed is:
 1. A semiconductor light device, comprising: asemiconductor substrate having a first conduction type; a first claddinglayer having the first conduction type and deposited above thesemiconductor substrate; an active layer deposited above the firstcladding layer; a second cladding layer having a second conduction typeand deposited above the active layer; and a contact layer deposited onthe second cladding layer, wherein the active layer includes a windowportion that is disordered via diffusion of vacancies, and a non-windowportion having less disordering than the window portion, the contactlayer includes a first region, and a second region that is below thefirst region and has greater affinity for hydrogen than the firstregion, the second region has a first hydrogen concentration in a regioncorresponding to the non-window portion, and a second hydrogenconcentration in a region corresponding to the window portion, the firsthydrogen concentration is higher than the second hydrogen concentration,and the first hydrogen concentration in the region corresponding to thenon-window portion is greater than 8.0E+16 atoms/cm³.
 2. Thesemiconductor light device according to claim 1, wherein the secondregion is formed at a lower growth temperature than a growth temperaturefor forming the first region.
 3. The semiconductor light deviceaccording to claim 1, wherein the first region includes a p-type GaAslayer doped with a first p-type dopant, the second region includes ap-type GaAs layer doped with a second p-type dopant, and the secondp-type dopant has greater affinity for hydrogen than the first p-typedopant.
 4. The semiconductor light device according to claim 3, whereinthe contact layer further includes a third region in which a dopingamount of the first p-type dopant is less than a doping amount of thefirst p-type dopant in the first region, and the second region isbetween the first region and the third region.
 5. The semiconductorlight device according to claim 3, wherein the first p-type dopantincludes Zn, Mg, or Be.
 6. The semiconductor light device according toclaim 3, wherein the second p-type dopant includes carbon.
 7. Thesemiconductor light device according to claim 3, wherein the totaldoping amount of the first and second p-type dopants in the contactlayer is no greater than 1.0E+15 atoms/cm².
 8. The semiconductor lightdevice according to claim 3, wherein a doping amount of the secondp-type dopant in the second region is less than a doping amount of thefirst p-type dopant in the first region.